Map of Highest Peak LeetCode solution in JavaScript

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var highestPeak = function (isWater) {
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  const RN = isWater.length,
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    CN = isWater[0].length;
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  const output = [...Array(RN)].map(() => Array(CN).fill(-1));
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  const dir = [
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    [1, 0],
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    [-1, 0],
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    [0, 1],
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    [0, -1],
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  ];
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  let queue = [];
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  for (let r = 0; r < RN; r++) {
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    for (let c = 0; c < CN; c++) {
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      if (isWater[r][c]) {
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        queue.push([r, c]);
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        output[r][c] = 0;
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      }
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    }
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  }
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  while (queue.length) {
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    const next = [];
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    for (let [r, c] of queue) {
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      for (let [dr, dc] of dir) {
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        dr += r;
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        dc += c;
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        if (dr < 0 || dc < 0 || dr >= RN || dc >= CN || output[dr][dc] !== -1)
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          continue;
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        output[dr][dc] = output[r][c] + 1;
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        next.push([dr, dc]);
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      }
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    }
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    queue = next;
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  }
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  return output;
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};